Process:
See Cooking Lentils and Legumes/Beans for cooking Rajma.
Heat oil to a sauce pan, add chopped ginger and onions. Sauté until onions are soft and golden brown.
Add chopped tomatoes, turmeric powder, cumin powder, garam masala powder and sauté until tomatoes become soft.
Add the cooked rajma , salt, 1 cup water and butter and simmer for 30 minutes. The longer you simmer the more the spices get into the rajma and the tastier it gets. You can alter the consistency of the gravy by adding more water.